All of the projects in this program investigate neoplastic disorders which fall into the following major groupings: 1. Breast cancer. The central studies of this disease focus on the role of endogenous and exogenous steroid hormones, specifically oral contraceptives, and conjugated estrogens. The hypothesis being tested is that a woman's breast cancer risk is determined, in part, by the proportion of her estrogens metabolized to estriol. Overall mortality is included in the health effects of contraceptives, and also being evaluated is the role of conjugated estrogens in the risk of cancer of the corpus uteri. 2. Hodgkin's disease. The hypothesis being tested is that Hodgkin's disease is transmitted by person-to-person contact. In the study of siblings, it was determined that if an infectious agent is responsible for communication of the disease, intimate and/or prolonged exposure is necessary. A further study on childhood environment was designed and separately funded for pursuit of etiologic factors of the disease. 3. Other studies include a case-control interview study to investigate the role of environmental factors in cancer of the pancreas, a study of the relationship of gastric ulcer to gastric cancer, and a study of benign breast disease and cancer of the endometrium. BIBLIOGRAPHIC REFERENCES: Cole, P., Brown, J.B. and MacMahon, B.: Oestrogen profiles of parous and nulliparous women. Lancet: 596-598, 18 September 1976. Morrision, A.S., Lowe, C.R., MacMahon, B., Ravnihar, B., and Yuasa, S.: Incidence risk factors and survival in breast cancer: Report on five years of follow-up observation. Europ. J. Cancer 13; 209-214, 1977.